The precise tracking of persons and/or objects is desirable in many applications. One way to achieve precision indoor location with electronic tracking systems is by ranging (estimating the distance) between one or more base stations and a mobile locator device. Known examples of electronic locating systems that perform ranging are GPS technology, in which satellite transmissions are used by mobile receivers to determine the position of the mobile receivers, and cell phone location systems, where tower-located base station receivers estimate the location of mobile hand-held cell phone transmitters.
However, in the past, several factors have hindered the use of known electronic locating systems in indoor environments. One major impediment to the use of known locator systems is multi-path signal contamination, referring to the signal scattering effect caused by the local environment between the transmitter and the receiver, such as walls and support beams. Other impediments include insufficient signal strength, lack of precision, the FCC spectrum non-compliance of ultra wide band systems, the need for pre-existing infrastructure, and failure of simple pulse distortion models in actual through-building and multi-path propagation conditions.